This invention pertains to a self-contained calibrator/irradiator and method for calibrating and irradiating large numbers of several types of personnel dosimetry equipment.
Operators of nuclear facilities employing large numbers of personnel have had a long standing requirement for calibrating (exposing to precisely known and reproducible fields of photon radiation, typically using 137 Cs as a source of radiation) film badges, thermoluminescent dosimeters, pocket dosimeters and electronic dosimeters. Typically these calibration procedures have been accomplished by exposing a radiation source, either manually or remotely using a calibrator in the center of a ring of dosimeters which may be 100 cm. to 120 cm. in diameter. The ring diameter will vary dependent on the dose rate to be delivered to the dosimeters Because dosimetric equipment has widely varying ranges, multiple dose rates are required to cover the full range of dosimeters regularly used.
The use of a radiation source, whether manually or remotely controlled, to calibrate dosimeters has required a dedicated room with typical minimum dimensions of 12'.times.12' which is essentially clear of other materials to reduce scattered radiation effect, from which all personnel must be evacuated while radiation (calibrations) is in progress and which typically requires shielded floor, walls and ceiling to reduce radiation in surrounding areas to levels in which personnel can be present during the irradiation.
Later versions have required huge lead shielding structures and, although they did not require an entire dedicated room, they were over 1.5 meters in diameter, weighed well over 1400 kg and certainly could not be considered portable in that, once set up in a given location, they were seldom or never moved. As a result of the foregoing, it became clear to the applicant that there was a need for a much smaller calibrator/irradiator which is truly portable.